One problem related to water pump has been reported for the 1996 Toyota 4Runner. The most recently reported issues are listed below.
Head gasket blew on 5vz-fe engine. This was exactly 3 years & 53k miles after the Toyota ssc (special service campaign) x01. In which they replaced the faulty head gaskets on my 4runner. Also replaced at the time were the; timing belt, water pump, & thermostat. The truck has had all of it's dealer/manufacturers recommended services and oil changes. Upon tear down the Toyota dealership found that both aluminum heads were cracked between the valves at 2-3 places.